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Local slopes of seismic events carry complete information about the
structure of the subsurface. We have developed a velocity-independent
-
imaging approach to perform moveout correction in 2D layered
VTI media. We process Radon-transformed data because
-
is the
natural domain for anisotropic parameter estimation in
vertically-variable media.
Effective VTI parameters turn into data attributes through the use of
slopes and are directly mappable to the zero-slope
traveltime. Interval parameters turn into data attributes as well. We
have developed the analytical theory for the slope-based Dix inversion
in
-
, as well as two alternative sets of equations that can be
regarded as an extension of Claerbout's method for
straightedge determination of interval velocity. Both sets of
equations exploit the intrinsic layer stripping power of the
-
domain to estimate interval parameters directly without involving
effective parameters.
The equations we have introduced to retrieve both effective and
interval parameters in VTI media require directly or indirectly an
estimation of the local data curvature.
On the other hand, Fowler's equations do not require an explicit use
of the curvature. Therefore, we propose bypassing the curvature
estimation by exploiting a curvature-independent estimation of the
zero-slope time
field that, together with the slopes,
provides the input to Fowler's method. The zero-slope time can be
found efficiently by employing the predictive painting algorithm. A
reference trace at the zero-slope time
is spread along the
local data slope to predict the
field along reflection curves
in the
-
CMP gather. This estimation appears robust and
efficient enough to enable automated, slope-based, dense estimation of
interval parameters.
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